Electronic Circuit Production

ABSTRACT

A system for continuous circuit fabrication comprising means for storing and dispensing ( 74 ) the substrate ( 2 ), means for laminating ( 1 ) the substrate ( 2 ), means for printing ( 76 ) the substrate ( 2 ), means for optical inspection ( 4 ) of the substrate ( 2 ), means for photolithography ( 6 ) of the substrate ( 2 ), means for drying ( 78 ) the substrate ( 2 ), means for developing ( 8, 16 ) the substrate ( 2 ), means for washing ( 10, 14 ) the substrate ( 2 ) and means for electroplating ( 82 ) the substrate ( 2 ).

FIELD OF THE INVENTION

The present invention relates to the fabrication of electronic circuitsand/or semiconductors on flexible substrates.

BACKGROUND OF THE INVENTION

As is known in the art, fabrication of circuitry usually involves thestages of deposition, removal, patterning and modification of electricalproperties. This process has been streamlined with the introduction ofreel-to-reel production for flexible substrates. Further to this,reel-to-reel fabrication processes are known in which an element of theprocess uses electrolysis, specifically electroplating of the conductivelayers of substrates.

US 2012/0305892 is concerned with an electronic device comprising anin-plane component formed in an organic semiconductor layer, desirablygraphene, on a flexible substrate, wherein the component is formed usingimprint lithography to create a trench through the organic semiconductorlayer in a roll-to-roll process, wherein the number of process stepsrequired is limited to allow manufacture of the device in a singleintegrated apparatus.

US 2004/0259365 is concerned with providing a polishing method and apolishing apparatus for appropriately controlling the potential of anacting electrode to perform an accurate and stable electrolyticpolishing process; there is also provided a method of manufacturing asemiconductor device using the polishing method and the polishingapparatus.

In the past, using electrolysis in the fabrication of electroniccircuits and/or semiconductors has been difficult to practicallyachieve. Specifically, it has been difficult to achieve a system designwhere an electrical voltage is applied to the conductive elements of thesubstrate. Further, in systems where the desired connection has beenachieved, it has previously been at the expense of the speed and therebyefficiency of the continuous processing of the system, for instancerequiring a separate stage in the fabrication process, where no otherprocessing is able to be undertaken, wherein the substrate is heldstationary and an electrode is steadily moved towards the substrate,thereby applying a voltage to the substrate.

As such, it would be beneficial in the field if a system design wereenvisaged in which the application of the voltage to the substrate, thatis turning the substrate into an electrode, were seamlessly integratedinto the fabrication process in a manner that required no extra stagesand no further time delay when added to the usual operation processes ofthe fabrication system. Stated another way, a system of such a designwould represent a saving of time, and thereby an increase in efficiency,over current fabrication processes that include an electrolysis stage.

Manufacturers are ever more concerned with the impact that theirprocesses may be having on the environment around them. However, it iscrucial that such concerns can be addressed within the context ofprofitable business. As such, innovations that can simultaneouslydecrease the adverse effects on the environment, whilst also increasingefficiency, represent vital contributions to the field.

STATEMENT OF THE INVENTION

The aspects of the present invention are defined by the accompanyingclaims.

According to one embodiment of the present invention, there is provideda means for the fabrication of flexible conductive circuitry within areel-to-reel production process.

BRIEF DESCRIPTION OF THE DRAWINGS

There now follows, by way of example only, a detailed description ofpreferred embodiments of the present invention, with reference to thefigures identified below.

FIG. 1 is a schematic cross-section of the apparatus in operation.

FIG. 2 is a schematic cross-section of the laminator unit, opticalinspection unit and photolithography unit.

FIG. 3 is a schematic cross-section of any one of the photoresistdevelopment unit, the post-development wash unit, the post-etch washunit or the photoresist removal unit.

FIG. 4 is a schematic cross-section of the conductive-layer etch unit.

FIG. 5 illustrates a section of the substrate.

FIG. 6 illustrates a section of the substrate which has a patternedlayer of material formed on the conductive side of the substrate.

FIG. 7 illustrates the action of the electrolytic process on both thesection of substrate and the electrode.

FIG. 8 illustrates a section of the substrate after the fabricationprocess.

FIG. 9 illustrates a process of redeposition.

FIG. 10 illustrates alternative components to be used in the fabricationprocess.

FIG. 11 illustrates the alternative embodiment of the fabricationprocess using the components of FIG. 10.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, functionally similar parts carry the samereference numerals between figures.

The present invention comprises a system for the production ofelectronic circuits or semiconductors onto flexible substrates. Inparticular, the system is an inline system, known in the art asreel-to-reel, whereby the process of fabrication can be said to becontinuous.

FIG. 1 illustrates a cross-section of the apparatus in operation. Thesystem has a laminator unit 1 that forms a substrate 2. The substrate 2exits the laminator unit 1 and is transported towards thephotolithography unit 6, and in doing so passes an optical inspectionunit 4. The substrate 2 is then transported to the photoresistdevelopment unit 8, before being further transported to thepost-development wash unit 10. Following this, the substrate 2 istransported to the conductive-layer etch unit 12, and subsequently thepost-etch wash unit 14. Finally, the substrate 2 is transported to thephotoresist removal unit 16, after which the substrate has beensuccessfully fabricated in preparation for the addition of electronicdevices or constructs. The operation of the individual units of thesystem will be further described below.

As an illustrative example, the conductor-coated substrate describedherein is most frequently referred to as ITO coated PET, however thoseskilled in the art will appreciate that this material could be anytransparent or non-transparent material such as one or more of ITO, ATO,gold, silver graphite, copper, graphene, zinc oxide, aluminium oxide,lead zirconium titanate, barium titanate and any other appropriatecoating that can be deposited on the substrate in a thin layer. Thematerial may be provided in one or more continuous or semi-continuousconductive coating or layer, and may comprise a plurality of such layersof the same or different materials, such as the materials mentionedabove. Similarly, the substrate can be any material that can be coatedwith a thin layer of conductive material, and in some cases theconductive material itself may also act as the substrate.

FIG. 2 illustrates a cross-section of the laminator unit 1, opticalinspection unit 4 and photolithography unit 6. The laminator 1 has asubstrate feed roller 18, which inputs the substrate base layer 19 intothe system Similarly, the dry etch resist feed roller 20 inputs the dryetch resist layer 21 into the system. The pressure and traction roller22 operates in conjunction with the heated pressure roller 24 to outputthe substrate 2 to the alignment rollers 26 at the exit of the laminatorunit 1.

The photolithography unit 6 has variable height rollers 30, supported byvariable height roller support arms 36, positioned at its entrance andexit. Within the photolithography unit 6 is a pattern design 32, whichis illuminated by an array of Ultra Violet (U.V.) light sources 28.

In operation, the laminator unit 1 is designed to physically combine theconstituent materials of a flexible substrate. This is achieved in auniform manner through the application of heat and pressure. To avoidcontamination by external elements, the laminator unit 1 is bothlight-sealed and dust-sealed, thereby protecting the light-sensitivematerials contained within. The laminator unit 1 is designed toaccommodate separate rolls for each of the constituent materials of aflexible substrate within it. For instance, the material that is to beused as the substrate base layer 19 would be fitted as a roll onto thesubstrate base feed roller 18. Similarly, the material to be used as thedry etch resist layer 21 would be fitted as a roll onto the dry etchresist feed roller 20. The material that is to be used as the substratebase layer 19 may be coated with a transparent conductive material ormaterials such as mentioned above. However, as will be appreciated bythose skilled in the art, the coating of the substrate base layer 19does not have to be transparent, and the substrate itself can be anymaterial that can be dispensed from as roll. Further, in some cases, theconductive material may itself form the substrate base layer 19. Whenactivated, the laminator unit 1 would act to simultaneously unwind thesubstrate base feed roller 18 and the dry etch resist feed roller 20, ata synchronized speed, ensuring that the rolls remain both wrinkle andair-bubble free. This action would feed both the substrate base layer 19and the dry etch resist layer 21 towards the pressure and tractionroller 22 and the heated pressure roller 24. The substrate base layer 19and the dry etch resist layer 21 intersect at a point directly betweenthe pressure and traction roller 22 and the heated pressure roller 24.At this intersection, the pressure and traction roller 22 applies alateral force from its surface into the substrate 2 along a planeperpendicular to the surface of the substrate 2. Simultaneously, theheated pressure roller 24 applies both heat, and a lateral force fromits surface into the substrate 2 along a plane parallel, but oppositelydirected, to the force applied by the pressure and traction roller 22.In this manner, the simultaneous action of the heat and pressureapplication acts to physically combine the substrate base layer 19 andthe dry etch resist layer 21 into a single flexible substrate 2,suitable for undergoing etching for the purpose of electronic circuitand/or semiconductor fabrication. Following this, the laminator unit 1outputs the newly formed substrate 2 through the alignment rollers 26,which are able to move along the vertical axis, and thereby act tocorrectly orientate the substrate 2 for the optical inspection process.

The substrate 2 is outputted from the laminator unit 1 towards thephotolithography unit 6 along a path 34. Before entering thephotolithography unit 6, the substrate 2 is subjected to an inspectionfor defects by an optical inspection unit 4. For instance, the opticalinspection unit 4 could comprise a camera system connected to aprocessor that is configured to inspect the substrate 2 for visibledefects following the lamination process of the laminator unit 1.Typical defects of interest include, but are not limited to, bubbles,wrinkles, creases, rips and overlaps, as well as any other marks thatcould affect the exposure process. In the event that a defect is locatedby the optical inspection unit 4, the processor system will notify theoperator and the substrate 2 will be moved past the area of defect, thusensuring only substrate that is not defected will continue to beprocessed by the setup as disclosed. This has the advantageous effect ofefficiently implementing resources, where no further processing in theproduction line is wasted on defective elements of the substrate,thereby saving electrical power, time and chemical resources.

Following optical inspection, the substrate 2 will be transported alongsubstrate path 34 into the photolithography unit 6 by the rotation ofthe adjustable height rollers 30, which also serve to maintain aconstant tension across the substrate 2. The substrate 2 will followsubstrate path 34 until it is correctly positioned over the patterndesign 32, which is fixed in location within the photolithography unit6. Once in location above the pattern design 32, the adjustable heightroller support arms 36 will retract downwards, moving the adjustableheight rollers 30 similarly downward, thereby pulling the substrate 2into contact with the pattern design 32. The pattern design 32 is apattern formed by the relative positioning of areas that are opaque, toareas that are transparent, and is arranged to form the design of thedesired final circuitry. With the substrate 2 now in contact with thepattern design 32, the U.V. light source array 28 is automaticallyactivated for a certain predetermined period of time, therebyilluminating the areas of the photoresist layer of the substrate thatare left exposed by the transparent areas of the pattern design 32. Bychemical processes known in the art, the areas of the photoresist layerof the substrate 2 that are illuminated by the U.V. light source array28 will undergo chemical changes in their material properties, leavingthese areas markedly altered in comparison with the areas of thephotoresist layer which were unexposed to the U.V. light. After theillumination is completed and the pattern has been transferred, theadjustable height roller support arms 36 will extend upwards, in turnmoving the adjustable height rollers 30, thereby taking the substrate 2and the pattern design 32 out of contact. Following this, the adjustableheight rollers 30 will rotate so as to transport the substrate 2 out ofthe photolithography unit 6 along substrate path 34.

The process as described above has been described within the context ofa specific example, namely that of positive photolithography. However,as will also be appreciated by those skilled in the art, the apparatusdisclosed in FIG. 2 could equally be used with, for instance, negativephotolithography, or other types of photolithography not hereindescribed.

FIG. 3 is an illustrative cross-section of any one of the photoresistdevelopment unit 8, the post-development wash unit 10, the post-etchwash unit 14 or the photoresist removal unit 16. Whilst the function ofeach of these units within the fabrication process is different, thedesign of the apparatus required to perform these functions issubstantially the same, with only the chemical composition of the fluid42 and the varying methods of operation being different. In order tofunction effectively, each tank 46 is both electrochemical and solventresistive, and is preferably, but not essentially, transparent for thepurpose of inspection. Within each tank 46 there is contained a fluid42, through which the substrate 2 travels along the substrate guide 40.To effect this movement, there are current carrying traction feedrollers 38 placed at the entrance of each tank 46, which are connectedto an electrical power source (not shown) by electrical connectors 44,and traction feed rollers 54 placed at the exit of each tank 46, whereinthe current carrying traction feed rollers 38 are used to ensure that anelectrical current is always present in the substrate 2. As thefabrication process herein described comprises a plurality of the tankunits shown in FIG. 3, each unit in the system is in electrical contactby virtue of the substrate 2. Hence, as certain tank units, namely theconductive-layer etch unit 12 of FIG. 4, involve the application ofvoltages in their operation, it is thereby necessary to apply voltagesto the remaining tank units in the system to directly oppose and therebyneutralize the voltages that may leak from the conductive-layer etchunit 12 into units of the system that do not require electrical currentin their operation. This is the purpose of the current carrying tractionfeed rollers 38. The tank 46 also has a cap 52 for refilling the fluid42, and a drain plug 50 for draining the fluid 42 from the tank 46. Alsowithin the tank 46 is a substrate guide roller 48, and an aerationsystem 56 placed on each interior wall of the tank 46. In an alternativeembodiment, the tank 46 may contain a plurality of substrate guiderollers 48, of substantially similar structure but varying size, whichwould enable the processing of longer sections of substrate 2. In afurther alternative, the traction feed roller 54 may be electricallyconnected, for example to collect digital reference information used toreference the location of the substrate 2 within the process.

In operation, the photoresist development unit 8 transports thesubstrate 2 into the entrance of the unit through the rotation of thecurrent carrying traction feed rollers 38. The electrical connectors 44provide an electrical voltage to the current carrying traction feedrollers 38, which serves to oppose and neutralise any voltages that maypropagate along the substrate 2 from other units in the system. Onentering the tank 46, the substrate 2 further enters a substrate guide40. The substrate guide 40 can be imagined to be physically andfunctionally similar to the guide tracks that a sliding door movesalong, as the substrate guide 40 merely brackets the sides of thesubstrate, leaving the top surface and bottom surface exposed to thefluid 42. As can be seen in FIG. 3, the substrate guide 40 traverses thefull length of the tank, taking the substrate 2 through a large volumeof the fluid 42. The substrate 2 is pulled through the fluid 42 throughthe rotational traction of the substrate guide roller 48 until such timeas the current carrying traction feed roller 38 comes into contact witha conductive area of the substrate 2 where there is no photoresistpresent, at which point the system sensors (not shown) detect that thesubstrate 2 is in the correct position, and the transportation of thesubstrate 2 is stopped.

As this is the photoresist development unit 8, the fluid 42 in this caseis a fluid suitable for developing the photoresist layer that wassubjected to UV light exposure in the photolithography unit 6, and willbe known by those skilled in the art. By virtue of the chemical changethat the areas of the substrate 2 that were exposed to UV light in thephotolithography unit 6 underwent, the developing fluid acts tochemically dissolve the photoresist layer of these areas, creating asuspension of the dissolved material in the fluid 42. This process ofdevelopment is aided by the introduction of air bubbles into the tank 46from the aeration system 56, which in acting like a physical stirrerserves to agitate the fluid sufficiently to increase the molecularreaction rate of the developing fluid on the photoresist layer of thesubstrate 2. This process leaves the top layer of the substrate 2 onlybearing the photoresist layer that was intended by the design. After thesubstrate 2 has moved through the tank 46, the traction feed rollers 54transport the substrate through the exit of the photoresist developmentunit 8 along path 34. Following the use of the photoresist developmentunit 8, when the setup is no longer in use, it is possible to drain thefluid 42 from the tank 46 by means of the drain plug 50. This leads tothe advantageous effect of being able to reclaim the material thatformerly comprised the photoresist layer of the substrate 2 that wasdissolved by the fluid 42 during the development process. In this waythe design can be seen to reduce the cost of materials in the process,and can thereby also be considered to be environmentally friendly.Before operation is intended to begin again, the fluid can be refilledthrough cap 52. This embodiment could be used in processes where anyother element of the substrate were to be removed (as opposed to justthose which were exposed to UV light), requiring only that in suchinstances a photoresist appropriate for such a process has been used.

In operation, the post-development wash unit 10 is substantially similarto the photoresist development unit 8 described above. In a fashionsimilar to that described above, the substrate 2 having been processedby the photoresist development unit 8 then enters the post-developmentwash unit 10, and is transported through the fluid 42. In the case ofthe post-development wash unit 10, the fluid 42 contained within is afluid suitable for the cleaning of the substrate 2, removing andneutralising any traces of developing fluid that may have remained onthe substrate 2 following the operation of the photoresist developmentunit 8. Further, the action of the cleaning fluid also removes anyfurther remnants of the photoresist layer that were intended to beremoved in the photoresist development unit 8. In a similar manner tothat of the photoresist development unit 8, the fluid can be drainedthrough drain plug 50, and any materials in suspension can be reclaimedfor reuse.

FIG. 4 is a schematic cross-section of the conductive-layer etch unit12. The design of the conductive-layer etch unit 12 is similar to thedesign of the tank of FIG. 3; however there are some essential featuresof distinction. The underlying feature that drives this distinction isthat the conductive-layer etch unit 12 is designed to exploit thephenomenon of electrolysis. In line with this operation, an electrode 58is attached to the cap 52, which projects downwards and into the fluid42. This electrode is provided with a DC electrical voltage of aparticular polarity by the electrical connector 60. The electrode ofopposite polarity is physically separated from the first electrode 58,and is here advantageously incorporated into the functionality of theelectrically polarized traction feed roller 55. The electricallypolarized traction feed roller 55 is provided with a DC voltage of apolarity opposite to the electrode 58, by means of the electricalconnector 62. In comparison with the setup of FIG. 3, the otherdistinction to be made is the lack of aeration system 56. Theseimportant differences aside, the form of the tanks are substantiallysimilar

In operation, the conductive-layer etch unit 12 of FIG. 4 pulls thesubstrate along path 34 and into the tank 46 by means of theelectrically polarized traction feed rollers 55. Following the processesof the previous stages, the substrate 2 arrives at the electricallypolarized traction feed rollers 55 with select areas of the conductivelayer exposed. As such, when the substrate 2 comes into contact with theelectrically polarized traction feed rollers 55, the electrical voltageas supplied by electrical connector 60 imparts a current of the samepolarity into the conductive layer of the substrate 2. The substrate 2then proceeds towards the fluid 42 by means of the rotation of thesubstrate guide roller 48. The tank 46 contains an electrolyte that isknown in the art. As would be appreciated by the person skilled in theart, this fluid should also be suitable for use with the conductivecompound to be removed from the substrate 2, as would be appropriate foran electrolytic process. The substrate 2 is brought into the fluid 42,whereby the process of electrolysis begins due to the electrical currentflowing into the fluid 42 from the electrode 58. Unlike conventionalelectrolytic processes within the art of conductive circuit fabrication,the process disclosed herein is that of electrolytic etching, wherebythe flow of material is from the substrate 2 to the fluid 42, therebyremoving material from the surface of the substrate 2. As such, uponentering the fluid 42, the conductive layer of the substrate 2 will beelectrically driven, by virtue of the potential difference createdbetween the electrode 58 and the conductive layer of the substrate 2from the electrically polarized traction feed roller 55, to give up ionsto constitute a flow of current through it. In this way, the conductivelayer will be gradually, but continually, depleted of its conductivelayer until the entire conductive layer is removed and charge ceases toflow, at which point the system sensors (not shown) will deem theprocess complete. At this point, the system sensors (not shown) detectthat current is no longer flowing within the conductive-layer etch unit12, and the substrate 2 is transported out of the tank 46 by the usualaction of the traction feed rollers 54 as described previously.Alternatively, only part of the conductive layer may be removed, and theelectrolytic etching may be halted after a predetermined time or ondetection of a predetermined condition. The current or voltage may bevaried so as to control the rate of electrolytic etching.

Following this process, at a time when the system is not in use, theelectrode 58 can be removed, and the conductive material that has beendeposited on it by the process of electrolysis can be disposed of safelyor recycled. In this way, an extremely high percentage of the materialremoved can be collected and reused. In the case of the system asdescribed above the electrolytic compound is oxalic acid highly dilutedwith ionized water, however those skilled in the art will appreciatethat the setup allows for the use of any other appropriate substance.

Referring to FIG. 3, in operation, the post-etch wash unit 14 issubstantially similar to the post-development wash unit 10 describedabove. In a fashion similar to that described previously, the substrate2 having been processed by the conductive-layer etch unit 12 then entersthe post-etch wash unit 14, and is transported through the fluid 42. Inthe case of the post-etch wash unit 14, the fluid 42 contained within isa fluid suitable for the cleaning of the substrate 2, removing andneutralising any traces of etching fluid that may have remained on thesubstrate 2 following the operation of the conductive-layer etch unit12. Further, the action of the cleaning fluid also removes any furtherremnants of the conductive layer that were intended to be removed in theconductive-layer etch unit 12. In a similar manner to that of thepost-development wash unit 10, the fluid can be drained through drainplug 50, and any materials in suspension can be reclaimed for reuse.

Referring to FIG. 3, in operation, the photoresist removal unit 16 issubstantially similar to the photoresist development unit 8 describedabove. In a fashion similar to that described previously, the substrate2 having been processed by the post-etch wash unit 14 then enters thephotoresist removal unit 16, and is transported through the fluid 42. Inthe case of the photoresist removal unit 16, the fluid 42 containedwithin is a fluid suitable for the removal of the final layer of thephotoresist that is still present on the substrate 2. This fluid willact to chemically dissolve the final remaining layer of photoresist thatis present on the substrate 2, after which only the conductive layer inthe design of the intended circuit, as applied in the photolithographyunit 6, remains on the surface of the substrate 2. This process leavesthe removed photoresist layer in suspension in the fluid 42. In asimilar manner to that of the post-development wash unit 10, the fluidcan be drained through drain plug 50, and any materials in suspensioncan be reclaimed for reuse. In a similar manner to that of thephotoresist development unit 8, the fluid can be drained through drainplug 50, and any materials in suspension, such as the removedphotoresist, can be reclaimed for reuse.

In the embodiments described above, the fabrication process has beendemonstrated in the context of discontinuous movement of the substrate 2through the system, wherein at certain points the substrate is held inplace whilst processing is completed. However, it will be appreciatedthat further embodiments, not included for conciseness, could beenvisaged where the motion of the substrate 2 is continuous throughoutthe system.

FIGS. 5 to 8 demonstrate the appearance of the flexible substrate atvarious stages in the fabrication process described above.

FIG. 5 illustrates a section of ITO coated PET 64 that can be used inthe above embodiments. However, as is true for all of the embodimentsherein, this material could be any transparent or non-transparentmaterial with a continuous or semi-continuous conductive coating, suchas described above. Similarly, the substrate can be any material thatcan be coated with a thin layer of conductive material, and in somecases the conductive material itself may also act as the substrate.

FIG. 6 illustrates a section of ITO coated PET 64, as in FIG. 5, whichhas a patterned layer of protective material 66 formed on the conductiveside of the substrate to protect select areas of the conductive layerfrom being removed when it is subjected to the patterning processdescribed in earlier embodiments. This is how the substrate appears onleaving the photoresist development unit 8, and also how it appearsafter washing in post-development wash unit 10 before enteringconductive-layer etch unit 12. Any substance that is used in thepatterning process must not remove the protective material layer 66, asthis would result in damage to the electronic circuit, as well as thepartial or complete removal of sections that are not desired to beremoved.

FIG. 7 illustrates a section of ITO coated PET where the ITO that is notprotected has migrated (represented by dashed arrows) from the surfaceof the PET to the electrode 58 in the manner previously described inrelation to the electrolytic action of the conductive-layer etch unit12. This migration of ITO results in the electrode 58 being covered by adeposited layer of ITO 68. Advantageously, almost all of the ITO that isremoved from the PET during this process can be reused in furtherprocesses, as will be described below.

FIG. 8 illustrates a section of ITO coated PET where the protectivecoating 66 has been removed revealing the desired pattern of conductivematerial 70. This is how the final substrate appears.

FIG. 9 illustrates a process of electroplating redeposition (82) that isan advantageous addition to the fabrication process described herein.This advantageous addition is only possible due to the distinguishingprocesses and embodiments described herein, which as previously stated,is unlike conventional electrolytic processes within the art ofconductive circuit fabrication as the process disclosed is that ofelectrolytic etching, whereby the flow of material is from the substrate2 to the fluid 42, thereby removing material from the surface of thesubstrate 2. As a result of this action, as previously described inrelation to the conductive-layer etch unit 12, there is a significantquantity of the conductive layer of the substrate 2 deposited on theelectrode 58. The setup disclosed in FIG. 9 seeks to advantageouslyexploit this feature.

In operation, the setup of FIG. 9 is envisaged to occur within a tankcalled the redeposition tank, that is substantially similar in design tothe conductive-layer etch unit 12 of FIG. 4. A section of ITO coated PETis shown, where the ITO that is collected on the electrode 68 is to bedeposited back onto the already patterned ITO by reversing the polarityof the electrical field as previously described in relation toconductive-layer etch unit 12. As such, the polarity of the fieldbetween the electrode 58 and the remaining ITO on the PET substrate 2,as effected by electrically polarised traction feed rollerssubstantially similar those number 55 in FIG. 4, will be reversed. Thisreversal in polarity of field will have the opposite effect of theelectrolytic process described in relation to FIG. 4, namely theconductive material deposited on the electrode 68 will be driven to giveup ions to constitute a reverse flow of current whereby the conductivematerial ends up being redeposited onto the conductive ITO that is lefton the PET substrate. This results in a substantially thicker layer ofconductive material 72 on the substrate 2. As the current continues toflow, redeposition will continue to occur until a state is reached thatis deemed to be sufficient by the system sensors (not shown). Thecurrent or voltage may be controlled so as to control the thickness ofthe redeposited material. Preferably, the applied voltage or current isDC (Direct Current) and the reversal of polarities occurs betweendiscrete steps of the deposition process.

This setup solves a number of problems, and thus represents a number ofadvantageous effects. Firstly, it is often in the manufacturer'sinterest to have a thin conductive layer on the substrate, as this isfaster to remove during fabrication. However, less conductive materialmakes for a much less efficient conductive surface, and subsequently aless efficient electronic circuit. This redeposition of conductivematerial onto the already present conductive material solves thisproblem, as in many cases a substantial amount of the conductivematerial needs to be removed or disconnected from the substrate to getthe pattern required, and so being able to reuse this conductivematerial by redeposition represents a significant advantageous increasein the conductivity, efficiency and durability of the resultingelectronic substrate.

Secondly, as the conductive material constitutes the most expensivecomponent of the substrate, the ability to recycle and redeposit itrepresents a significant advantageous saving in cost.

This process can be implemented with the previous embodiments of thedisclosure in a number of manners. For instance, a setup as seen in FIG.1 can be envisaged whereby following the photoresist removal unit 16there is a redeposition tank substantially similar to theconductive-layer etch unit 12, where in operation the electrode ismechanically moved (by machinery not shown here) between theconductive-layer etch unit 12 and said redeposition tank to alternatelyremove and collect the conductive layer material during the etchingprocess at conductive-layer etch unit 12, and then deposit the collectedconductive layer back onto the substrate in said redeposition tank.Alternatively, a setup could be envisaged where computer systems (notdescribed here) could be used reverse the direction of the substratethrough the system, wherein an area of substrate having been through theentire fabrication process up to immersion in the photoresist removalunit 16, could then be realigned into the conductive-layer etch unit 12,which then has its electrical polarity reversed relative to its originaloperation, thereby constituting a redeposition of conductive material aspreviously described. For this system to work, it is evident that thenature of the chemicals chosen to be used in each of the tank units needto be of a type that does not in any way damage or effect the state ofthe substrate when the system is run in reverse, where the substratemoves backward through tanks by which it has already been processed. Theperson skilled will appreciate this and be able to achieve a suitablesetup using known methods.

These exemplary embodiments are to be seen as merely illustrative andnot limiting of the manner in which the setup of FIG. 9 could beimplemented within the fabrication process as disclosed herein. It willbe appreciated that further embodiments, not included for conciseness,could be envisaged.

FIG. 10 illustrates an alternative embodiment in which the laminatorunit 1 and the photolithography unit 6 of all previous embodiments arereplaced by alternative units, as described below. The replacement ofthese two units by alternative units is the only distinction over theprevious embodiments, and so it can be seen that these two units canmerely be combined with all previously disclosed embodiments in place ofthe laminator unit 1 and the photolithography unit 6. A roll of PETcoated with ITO 74 is positioned in such a way such that the substrate 2is in a location that is advantageous to the dispensing of the material.An inkjet printer 76 is supplied with the pattern that is to be made onthe substrate (in a process known in the art and not described here).The optical inspection unit 4 is identical in form and function to thatpreviously described. An Infra-Red (IR) drying unit 78, containingmultiple IR sources 80, is used to fix the ink that has been dispensedby the printer (in a process known in the art and not described here).The inkjet printer 76 may be replaced by an inline silk screen printer,a flexographic printer or any other printing possesses that are able todispense the type of material used as a protection layer for theconductive material.

FIG. 11 is an illustration of the fabrication system using thealternative components as shown in FIG. 10 and described above.

Alternative Embodiments

The embodiments described above are illustrative of, rather thanlimiting to, the present invention. Alternative embodiments apparent onreading the above description may nevertheless fall within the scope ofthe invention.

Reference Numerals 1-laminator unit 2-substrate 4-optical inspectionunit 6-photolithography unit 8-photoresist development unit10-post-development wash unit 12-conductive-layer etch unit 14-post-etchwash unit 16-photoresist removal unit 18-substrate base feed roller19-substrate base layer 20-dry etch resist feed roller 21-dry etchresist layer 22-pressure and traction roller 24-heated pressure roller26-alignment rollers 28-U.V. light source array 30-adjustable heightrollers 32-pattern design 34-substrate path 36-adjustable height rollersupport arm 38-current carrying traction feed rollers 40-substrate guide42-process-specific fluid 44-electrical connectors 46-tank(electrochemical and solvent resistive) 48-substrate guide roller50-drain plug 52-cap 54-traction feed roller 55-electrically polarisedtraction feed roller 56-aeration system 57-traction feed rollers58-electrode 60-electrical connector 62-electrical connector 64-ITOcoated PET 66-protective material layer 68-deposited layer of ITO70-desired pattern of conductive material 72-thick layer of redepositedconductive material 74-substrate roll 76-inkjet printer 78-IR dryingunit 80-IR sources 82-electroplating redeposition

1. An electrolytic etching and/or deposition system (12), comprising: a.a container (46) for an electrolyte (42); b. means (55) for moving acontinuous section of substrate (2) through the electrolyte (42); c. afirst electrode (58) arranged to be in electrical contact with theelectrolyte (42), and d. a second electrode (62) arranged to be inelectrical contact with the substrate (2), so as to etch or deposit alayer of the substrate (2) by electrolysis.
 2. The electrolytic etchingsystem (12) of claim 1, wherein the second electrode (62) is arranged tobe in electrical contact with the substrate (2) via the means (55) formoving the continuous section of substrate (2) through the electrolyte(42).
 3. The electrolytic etching system of claim 2, wherein the means(55) for moving the continuous section of substrate (2) through theelectrolyte (42) comprises a feed roller.
 4. The electrolytic etchingsystem (12) of any preceding claim, wherein the polarities of the firstelectrode (58) and second electrode (62) are reversible so as toincrease the thickness of the etched layer of the substrate (2) byelectrolysis.
 5. The electrolytic etching system (12) of any precedingclaim, wherein the first electrode (58) is removable from the container(46).
 6. The electrolytic etching system (12) of claim 5, wherein thefirst electrode (58) is attached to a removable section (52) of thecontainer (46).
 7. The electrolytic etching system (12) of any precedingclaim, wherein the container (46) includes a drain (50) for draining theelectrolyte (42).
 8. The electrolytic etching system (12) of anypreceding claim, wherein the container (46) includes a guide (40) forguiding the continuous section of the substrate (2).
 9. A system forcontinuous circuit fabrication, comprising the electrolytic etchingand/or deposition system (12) of any preceding claim, and furthercomprising one or more of: means for storing and dispensing (74) thesubstrate (2), means for laminating (1) the substrate (2), means forprinting (76) the substrate (2), means for optical inspection (4) of thesubstrate (2), means for photolithography (6) of the substrate (2),means for drying (78) the substrate (2), means for developing (8, 16)the substrate (2), means for washing (10, 14) the substrate (2) andmeans for electroplating (82) the substrate (2).
 10. A method ofelectrolytic etching, comprising: a. introducing a continuous section ofsubstrate (2) into an electrolyte (42); and b. applying a voltagebetween a first electrode (58) in electrical contact with theelectrolyte (42) and a second electrode (62) in electrical contact withthe substrate (2), so as to etch the substrate (2) by electrolysis. 11.The method of claim 10, wherein the second electrode (62) is inelectrical contact with the substrate (2) via means (55) for introducingthe continuous section of substrate (2) through the electrolyte (42).12. The method of claim 10 or 11, wherein at a subsequent time thepolarities of the first electrode (58) in electrical contact with theelectrolyte (42) and a second electrode (62) in electrical contact withthe substrate (2) are reversed so as to increase the thickness of theetched layer of the substrate (2) by electrolysis.
 13. A method ofelectrolytic deposition, comprising: a. introducing a continuous sectionof substrate (2) into an electrolyte (42), wherein the substrateincludes an exposed conductive layer (70); and b. applying a voltagebetween a first electrode (58) in electrical contact with theelectrolyte (42) and a second electrode (62) in electrical contact withthe exposed conductive layer (70), so as to increase the thickness ofthe exposed conductive layer (72) by electrolysis.